Polishing pad, use thereof and method for making the same

ABSTRACT

The present invention mainly relates to a polishing pad that comprises a buffer sheet, a polishing sheet and adhesive for adhering the buffer sheet to the polishing sheet. The buffer sheet comprises fibers. The polishing sheet comprises a first elastomer. The adhesive comprises a second elastomer. A method of polishing a substrate comprising using the polishing pad and a method for manufacturing the polishing pad described above are also provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing pad for use in chemical mechanical polishing.

2. Description of the Related Art

Chemical mechanical polishing (CMP) is a procedure for planarizing the surface of a substrate with a polishing pad. CMP is generally applied in polishing lenses, mirrors, substrates of liquid crystal displays, silicon wafers, and oxidation and/or metal layers on silicon wafers.

Taking silicon wafers as an example, ingots of monocrystalline silicon are sliced first. The wafers are usually lapped to make them flat for subsequently chemical etching. A polishing process is required after the etching process. During the polishing process, a polishing pad together with slurry reacts chemically with the silicon atoms on the surface of the wafer to make the reacted surface softer than the underlying silicon.

Furthermore, the reacted surface is continually wiped away, causing fresh silicon to be exposed to the slurry and the polishing pad.

U.S. Pat. No. 6,358,130 discloses a conventional polishing pad for use with a polishing fluid. The conventional polishing pad has a polishing layer and a window in an opening through the polishing layer. The undersurfaces of the polishing layer and window are covered by an underlying fluid-impermeable layer. The conventional polishing pad further comprises an adhesive on the fluid-impermeable layer forming respective bond seals between the polishing layer and the window and a lower backing layer. The adhesive and the fluid impermeable layer resist wetting of an interface between the adhesive and each of the polishing layer and the window and the fluid-impermeable layer in the conventional polishing pad. An advantage is that the fluid-impermeable layer, being uninterrupted, avoids a tendency to produce leakage paths due to bending during routine handling, or due to exertion of polishing pressure during use of the polishing pad, or due to small voids or gaps in the adhesive. A further advantage is that the bond seals minimize wetting by the polishing fluid of the interface between the adhesive and each of the polishing layer, the window and the fluid-impermeable layer.

Because the lower backing layer of the conventional polishing pad usually comprises fibers, contents of the lower backing layer are not distributed evenly. Also, because the polishing layer of the conventional polishing pad usually comprises elastomers, contents of the polishing layer are not distributed evenly either. The variations of the thickness of the lower backing layer and polishing pad are easily observed. Besides, the surfaces of the lower backing layer and the polishing pad are not flat and usually rough and undulating. Such features make it difficult for the lower backing layer or polishing pad to attach tightly and completely to the fluid-impermeable layer. Bubbles and vacant space are easily observed in the interface between the lower backing layer and the polishing layer and the fluid-impermeable layer (as shown in FIG. 1). As a result, the slurry easily permeates into the interface between the lower backing layer and the polishing layer and the fluid-impermeable layer via the bubbles and vacant space. Therefore, the lifespan of the conventional polishing pad is shortened. The effect and efficiency of chemical mechanical polishing are both reduced thereby.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a polishing pad that comprises a buffer sheet, a polishing sheet and adhesive for adhering the buffer sheet to the polishing sheet. The buffer sheet comprises fibers. The polishing sheet comprises a first elastomer. The adhesive comprises a second elastomer.

Another object of the present invention is to provide a method of polishing a substrate comprising using the polishing pad described above to polish a surface of the substrate.

Still another object of the present invention is to provide a method for manufacturing the polishing pad described above comprising the steps

-   -   (a) providing the buffer sheet and the polishing sheet;     -   (b) applying the second elastomer on a surface of the buffer         sheet or the polishing sheet; and     -   (c) adhering the buffer sheet to the polishing sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a view under a transmission electron microscope of the conventional polishing pad.

FIG. 2 illustrates a view under a transmission electron microscope of the polishing pad according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is to provide a polishing pad that comprises a buffer sheet, a polishing sheet and adhesive for adhering the buffer sheet to the polishing sheet. The buffer sheet comprises fibers. The polishing sheet comprises a first elastomer. The adhesive comprises a second elastomer.

According to the invention, any buffer sheet comprising fibers can be applied in the invention. The buffer sheet preferably comprises a non-woven fabric, and more preferably, the buffer sheet comprises a rolled non-woven woven fabric. The rolled nonwoven fabric can be used in a roll-to-roll way that improves batch uniformity in comparison with a conventional method of producing a single polishing pad involving molding or casting.

As used herein, “a non-woven fabric” refers to a manufactured sheet, web or mat of directionally or randomly orientated fibers, bonded by friction, and/or cohesion and/or adhesion, excluding paper and products which are woven, knitted, tufted, stitch-bonded incorporating binding yarns or filaments, or felted by wet-milling, whether or not additionally needled. The fibers may be of natural or man-made origin. They may be staple or continuous filaments or be formed in situ. Depending on the method of forming the web, the nonwoven fabric usually comprises a composite nonwoven fabric, a needle-punched nonwoven fabric, a melt-blown nonwoven fabric, a spunbonded nonwoven fabric, a dry-laid nonwoven fabric, a wet-laid nonwoven fabric, a stitch-bonded nonwoven fabric, or a spunlace nonwoven fabric. Compared with woven fabric, non-woven fabric has a better material property.

As used herein, the term “(a) fiber(s)” refers to a single fiber or composite fibers, preferably composite fibers. The fiber is selected in accordance with a substrate to be polished. Preferably, the fiber is made of at least one material selected from the group consisting of polyamide, terephthalamide, polyester, polymethyl methacrylate, polyethylene terephthalate, polyacrylonitrile, and a mixture thereof.

As used herein, the term “a first elastomer,” also known as “a first elastic polymer,” refers to a type of polymer that exhibits a rubber-like quality. When polishing, the first elastomer serves as a good buffer to avoid scraping the surface of the substrate to be polished. In one preferred embodiment of the invention, the first elastomer comprises a foam resin. As used herein, the term “a foam resin” refers to a material containing a thermoplastic resin and a thermodecomposing foaming agent. The first elastomer preferably comprises at least one selected from the group consisting of polyurethane, polyolefin, polycarbonate, polyvinyl alcohol, nylon, elastic rubber, polystyrene, polyaromatic molecules, fluorine-containing polymer, polyidmide, cross-linked polyurethane, cross-linked polyolefin, polyether, polyester, polyacrylate, elastic polyethylene, polytetrafluoroethylene, poly(ethylene terephthalate), polyaromatic amide, polyarylalkene, polymethyl methacrylate, a copolymer thereof, a block copolymer thereof, a mixture thereof, and a blend thereof; more preferably, the first elastomer comprises polyurethane.

In one preferred embodiment of the invention, the polishing sheet further comprises fibers, and more preferably, the fibers comprise a non-woven fabric, as described above. The fiber polishing sheet provides protrusions for polishing and also provides a scaffold allowing elastomers of a polishing sheet to be deposited in the space defined by the scaffold. Artisans skilled in this field can choose suitable kinds of fibers and coordinate the first elastomer with the fibers according to the disclosure of the specification. The fiber is preferably made of at least one material selected from the group consisting of polyamide, terephthalamide, polyester, polymethyl methacrylate, polyethylene terephthalate, polyacrylonitrile, and a mixture thereof.

In one more preferred embodiment of the invention, the polishing sheet comprises a plurality of continuous pores embedded in the fibers and the first elastomer. The continuous pores of the polishing pad have an even size, which benefit the flow of polishing fluid and distribution of polishing particles and removal of polishing residues. In a preferred embodiment of the invention, the continuous pores have a pore size ranging from 0.1 μm to 500 μm.

The adhesive according to the invention is formed between the buffer sheet and the polishing sheet and preferably embedded into the fibers of the buffer sheet. Because the adhesive according to the invention is preferably embedded into the fibers of the buffer sheet, it serves as an intermediate between the buffer sheet and the polishing sheet. The adhesive according to the invention is designed to modify the surface of the buffer sheet and the polishing sheet, and is able to fill rough and undulating points of the buffer sheet and the polishing sheet (as shown in FIG. 2). Therefore, these two sheets can be adhered to each other well. The adhesion strength of the buffer sheet and the polishing sheet is dramatically enhanced. Moreover, the polishing pad according to the invention works without slurry permeating it. The lifespan of the polishing pad is lengthened. The effect and efficiency of chemical mechanical polishing are both improved thereby.

As used herein, the term “a second elastomer,” also known as “a second elastic polymer,” refers to a type of polymer that exhibits rubber-like qualities. The second elastomer serves as adhesive for adhering the buffer sheet to the polishing sheet. In one preferred embodiment of the invention, the second elastomer is paste. In one more preferred embodiment of the invention, the second elastomer comprises at least one selected from the group consisting of polyurethane, polyvinyl chloride, polystyrene, polyethylene, polyamide, polyether, polypropylene, ethylene/vinyl acetate, a copolymer thereof, a block copolymer thereof, a mixture thereof, and a blend thereof. In one most preferred embodiment of the invention, the second elastomer comprises polyurethane.

In one preferred embodiment of the invention, the adhesive is two-component paste. The two-component paste refers to paste comprising two components that interact or cross-link with each other to achieve the adherence effect. The two-component paste preferably comprises the second elastomer and polyisocyanate.

The present invention also provides a method of polishing a substrate comprising using the polishing pad mentioned above to polish a surface of the substrate.

The present invention also provides a method for manufacturing the polishing pad described above comprising the steps of:

-   -   (a) providing the buffer sheet and the polishing sheet;     -   (b) applying the second elastomer on a surface of the buffer         sheet or the polishing sheet; and     -   (c) adhering the buffer sheet to the polishing sheet.

The manner of adhering the buffer sheet to the polishing sheet varies according to the form of the adhesive. The adhesive for adhering the buffer sheet to the polishing sheet is preferably applied on at least one surface of the buffer sheet and the polishing sheet by coating, spraying, printing or scraping.

After applying the adhesive, the buffer sheet and the polishing sheet are adhered together. The buffer sheet and the polishing sheet are preferably adhered to each other at a temperature from 75° C. to 80° C.

If necessary, after step (c) according to the invention, the method further comprises a curing step. In some cases, the adhesive needs the curing step to solidify and form the bonding. The condition and manner of the curing step varies according to the adhesive used.

The following examples are given for the purpose of illustration only and are not intended to limit the scope of the present invention.

Conventional polishing pad: A lower backing layer and the polishing layer are adhered to a fluid-impermeable layer with adhesive.

Polishing pad according to the invention: A buffer sheet and a polishing sheet are adhered together with adhesive comprising polyurethane.

The properties of the conventional polishing pad (Pad 1) and the polishing pad according to the invention (Pad 2) are shown in Table 1.

TABLE 1 Adhering Strength Dry (kg/cm) Wet (kg/cm) Pad 1 0.42 0.35 Pad 2 1.1 0.9

(R.R)avg: 6277.7005

NU %. 0.0568894

Equipment: IPEC776

While embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by persons skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention is not limited to the particular forms as illustrated, and that all the modifications not departing from the spirit and scope of the present invention are within the scope as defined in the appended claims. 

1. A polishing pad comprising: a buffer sheet comprising fibers; a polishing sheet comprising a first elastomer, said polishing sheet comprising a polishing surface for polishing a substrate; and adhesive for adhering the buffer sheet to the polishing sheet, the adhesive comprising a second elastomer, wherein the second elastomer comprises at least one selected from the group consisting of polyvinyl chloride, polystyrene, polyethylene, polyamide, polyether, polypropylene, ethylene/vinyl acetate, a copolymer thereof, a block copolymer thereof, a mixture thereof, and a blend thereof.
 2. The polishing pad according to claim 1, wherein the buffer sheet comprises a non-woven fabric.
 3. The polishing pad according to claim 1, wherein the fibers are selected from the group consisting of a single fiber and composite fibers.
 4. The polishing pad according to claim 1, wherein the fibers are made of at least one material selected from the group consisting of polyamide, tereplithalamide, polyester, polymethyl methacrylate, polyethylene terephthalate, polyacrylonitrile, and a mixture thereof.
 5. The polishing pad according to claim 1, wherein the first elastomer comprises a foam resin.
 6. The polishing pad according to claim 1, wherein the first elastomer comprises at least one selected from the group consisting of polyurethane, polyolefin, polycarbonate, polyvinyl alcohol, nylon, elastic rubber, polystyrene, polyaromatic molecules, fluorine-containing polymer, polyidmide, cross-linked polyurethane, cross-linked polyolefin, polyether, polyester, polyacrylate, elastic polyethylene, polytetrafluoroethylene, poly(ethylene terephthalate), polyaromatic amide, polyarylalkene, polymethyl methacrylate, a copolymer thereof, a block copolymer thereof, a mixture thereof, and a blend thereof.
 7. The polishing pad according to claim 6, wherein the first elastomer comprises polyurethane.
 8. The polishing pad according to claim 1, wherein the polishing sheet comprises fibers.
 9. The polishing pad according to claim 8, wherein the fibers in the polishing sheet comprise a non-woven fabric.
 10. The polishing pad according to claim 8, wherein the fibers in the polishing sheet are selected from the group consisting of a single fiber and composite fibers.
 11. The polishing pad according to claim 8, wherein the fibers in the polishing sheet are made of at least one material selected from the group consisting of polyamide, terephthalamide, polyester, polymethyl methacrylate, polyethylene terephthalate, and polyacrylonitrile, and a mixture thereof.
 12. The polishing pad according to claim 8, wherein the polishing sheet comprises a plurality of continuous pores embedded in the fibers and the first elastomer.
 13. (canceled)
 14. The polishing pad according to claim 12, wherein the second elastomer comprises polyurethane.
 15. The polishing pad according to claim 1, wherein the adhesive is selected from the group consisting of single-part adhesive, two-part adhesive and wet solidification adhesive.
 16. The polishing pad according to claim 15, wherein the two-part adhesive comprises the second elastomer and polyisocyanate.
 17. A method of polishing a substrate comprising using the polishing pad according to claim 1 to polish a surface of the substrate.
 18. A method for manufacturing the polishing pad according to claim 1, comprising the steps of: (a) providing the buffer sheet and the polishing sheet; (b) applying the second elastomer on a surface of the buffer sheet or the polishing sheet; and (c) adhering the buffer sheet to the polishing sheet.
 19. The method according to claim 18, wherein step (b) comprises coating, spraying, printing or scraping the second elastomer on a surface of the buffer sheet or the polishing sheet.
 20. The method as claimed in claim 18, which after step (c) further comprises a curing step. 